The proximity fuse comprises a transmitter for transmitting electromagnetic radiation towards a target and a receiver for receiving the transmitted electromagnetic radiation which is reflected towards the receiver. By electromagnetic radiation it is meant preferably but not exclusively optical light. A reference plane is defined as the plane in which electromagnetic radiation emitted from the transmitter towards the target is transmitted between the transmitter and the receiver.
When the radiation lobe of the transmitter covers a target or parts of a target, the target or an area of the target is imaged as a spot on a detector in the receiver. An electrical signal is received at the detector output which varies as a function of the distance to the target and the capability of the target surface to reflect the electromagnetic radiation emitted by the transmitter. The electrical signal can be compared with a fixed reference level and when this is exceeded, the proximity fuse thereby delivers an output signal which can be utilized by the launchable unit for a weapon charge, as an example.
Active proximity fuses of the type specified above are already known, and in this connection reference can be made, for example, to SE B 458 480.
The operation of the proximity fuse can be disturbed by spherical particles which occur in the atmosphere. Examples of such particles are water drops in haze, fog and clouds. These particles reflect some of the electromagnetic radiation emitted by the transmitter of the proximity fuse towards the receiver of the proximity fuse. This makes it more difficult to distinguish the radiation reflected by the target and the accuracy of detection is impaired.